1. Field of the Invention
The invention relates to cyclic silazanes, to a process for the preparation thereof, and to reactions thereof with water and alcohols.
2. Background Art
Cyclic silazanes can be used, for example, as precursors for the preparation of aminoalkyl-terminated polysiloxanes. If cyclic silazanes are hydrolyzed as described in DE-A-3546376, bisaminoalkyl-terminated disiloxanes are obtained: 
DE-A-3546376 also discloses cyclic silazanes which are prepared by intramolecular hydrosilylation, in particular N-substituted silazanes which carry an SiY2H group as a substituent, where Y is a hydrocarbon radical. The hydrolysis of these silazanes also gives, besides the desired bisaminoalkyl-terminated disiloxanes, monoamino-alkyl-substituted disiloxanes and unsubstituted tetraalkyldisiloxanes: 
Z is as defined for Y.
Cyclic silazanes which are silyl-substituted on the nitrogen were described for the first time in U.S. Pat. No. 3,146,250. The silyl substituents have the general formula I
SiY2xe2x80x94Rxe2x80x2xe2x80x94Xxe2x80x83xe2x80x83(I)
where Y is a hydrocarbon radical, Rxe2x80x2 is a divalent hydrocarbon, and X is a halogen atom having an atomic weight of greater than 35 daltons. The hydrolysis of these silyl-substituted cyclic silazanes also gives, besides the desired bisaminoalkyl-terminated disiloxanes, monochloroalkyl-substituted disiloxanes and bischloroalkyl-substituted disiloxanes.
The invention relates to cyclic silazanes of the general formula II 
in which
R is a divalent, Sixe2x80x94Cxe2x80x94 and Cxe2x80x94N-bound, optionally cyano- or halogen-substituted C3-C15-hydrocarbon radical, in which one or more non-adjacent methylene units may be replaced by xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94OCOOxe2x80x94, xe2x80x94Sxe2x80x94 or xe2x80x94NRXxe2x80x94 groups and in which one or more non-adjacent methine units may be replaced by xe2x80x94Nxe2x95x90, xe2x80x94Nxe2x95x90Nxe2x80x94 or xe2x80x94Pxe2x95x90 groups, where at least 3 and at most 6 atoms are arranged between the silicon atom and the nitrogen atom of the ring,
R2 is a hydrogen atom or a monovalent, optionally cyano- or halogen-substituted, Sixe2x80x94C-bound C1-C20-hydrocarbon radical or C1-C20-hydrocarbonoxy radical, in each of which one or more non-adjacent methylene units may be replaced by xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94OCOOxe2x80x94, xe2x80x94Sxe2x80x94 or xe2x80x94NRxxe2x80x94 groups, in which one or more non-adjacent methine units may be replaced by xe2x80x94Nxe2x95x90, xe2x80x94Nxe2x95x90Nxe2x80x94 or xe2x80x94Pxe2x95x90groups, and wherein
Rx is hydrogen or an optionally halogen-substituted C1-C10-hydrocarbon radical, and
The compounds of the general formula II contain two Si-alkyl-nitrogen radicals and no Si-alkyl-halogen radical. The compounds of the general formula II are then hydrolyzed, forming bisaminoalkyl-terminated disiloxanes of the general formula III in high yields and essentially without further by-products: 
This process for the preparation of bisaminoalkyl-terminated disiloxanes of the general formula III is likewise a subject-matter of the invention.
R may be aliphatically saturated or unsaturated, aromatic, straight- chain or branched. R is preferably an unbranched C3-C4-alkylene radical, which may be substituted by halogen atoms, in particular, fluorine and/or chlorine.
The C1-C20-hydrocarbon radicals and C1-C20-hydrocarbonoxy radicals R2 may be aliphatically saturated or unsaturated, aromatic, straight-chain or branched. R2 preferably has 1 to 12 atoms, in particular 1 to 6 atoms, preferably only carbon atoms, or one alkoxy oxygen atom and otherwise only carbon atoms. R2 is preferably a straight-chain or branched C1-C6-alkyl radical. Particular preference is given to the radicals methyl, ethyl, phenyl, vinyl and trifluoropropyl.
Particular preference is given to the compounds in which R is a propylene radical and R2 is a methyl, ethyl, phenyl, vinyl or trifluoropropyl radical.
The compounds of the general formula II may be reacted with alcohols of the general formula R3xe2x80x94OH, forming aminoalkyl-terminated dialkylalkoxysilanes of the general formula VI, likewise in high yields and also essentially without further by-products. 
R2 and R here are as defined above, and R3 is a monovalent, optionally cyano- or halogen-substituted C1-C20-hydrocarbon radical, in which one or more non-adjacent methylene units may be replaced by xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94 or xe2x80x94OCOOxe2x80x94 groups, xe2x80x94Sxe2x80x94 or xe2x80x94NRxxe2x80x94 where Rx is as defined above, and in which one or more non-adjacent methine units may be replaced by xe2x80x94Nxe2x95x90, xe2x80x94Nxe2x95x90Nxe2x80x94 or xe2x80x94Pxe2x95x90 groups and may optionally carry further OH groups. This process for the preparation of aminoalkyl-terminated dialkylmethoxysilanes of the general formula III is likewise a subject-matter of the invention.
R3 is preferably methyl, ethyl, isopropyl or methoxymethyl.
The invention furthermore relates to a process for the preparation of the cyclic silazanes of the general formula II in which a haloalkyldialkylchlorosilane of the general formula IV 
or bis(haloalkyl)tetraalkyldisilazane of the general formula V 
or a mixture of compounds of the general formulae IV and V, in which
x is F, Cl, Br or I,
R1 is a hydrogen atom or a monovalent, optionally halogen-substituted, Sixe2x80x94C-bound C1-C15-hydrocarbon radical in which in each case one or more non-adjacent methylene units may be replaced by xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94 or xe2x80x94OCOOxe2x80x94 groups or xe2x80x94Sxe2x80x94 and in which one or more non-adjacent methine units may be replaced by xe2x80x94Nxe2x95x90, xe2x80x94Nxe2x95x90Nxe2x80x94 or xe2x80x94P= groups, and
R2 and R are as defined above, is reacted with ammonia.
The process disclosed in DE-A-3546376 for the preparation of silazanes which are silyl-substituted on the nitrogen uses expensive starting materials which are difficult to prepare. The process described in U.S. Pat. No. 3,146,250 gives only low yields of the desired product. By contrast, the above process gives the compounds of the general formula II inexpensively, i.e. from inexpensive starting materials and in high yields.
A characterizing feature of this process is that the ammonia in this process is simultaneously reactant, but also acceptor for the hydrogen halide liberated and, at sufficient pressure, is additionally also a solvent. The ammonia is therefore employed in stoichiometric amounts or in excess, based on the compounds of the general formulae IV and V. Preference is given to a 10- to 140-fold molar excess, particularly preferably to a 30- to 70-fold molar excess.
In order to accelerate the reaction, catalysts may optionally be added, for example metal halides such as sodium iodide or potassium iodide. In a preferred embodiment, the reaction components should be actively mixed. In order to ensure good mixing of the reaction components, the reaction can be carried out, for example, with stirring. The reaction temperature is limited at the lower end by the solubility of the reaction components and at the upper end by the decomposition temperatures of the starting materials and products. The process is preferably carried out at from 0xc2x0 C. to 150xc2x0 C., preferably at above room temperature. A reaction temperature of at least 40xc2x0 C., in particular at least 60xc2x0 C., is particularly preferred.
It is advantageous to carry out the reaction at a superatmospheric pressure of from 1.1 to 1000 bar. In a preferred embodiment, the pressure is at least 20 bar. The pressure can varied by admixing an inert gas if desired. The compounds of the general formula II are isolated and purified by known industrial methods, such as, for example, filtration, extraction or distillation. The compounds prepared in this way can be handled in the usual manner.
The process can be carried out in the presence or absence of aprotic solvents. If aprotic solvents are used, solvents or solvent mixtures having a boiling point or boiling range of up to 120xc2x0 C. at 0.1 MPa are preferred. Examples of such solvents include ethers such as dioxane, tetrahydrofuran, diethyl ether, diisopropyl ether and diethylene glycol dimethyl ether; chlorinated hydrocarbons such as dichloromethane, trichloromethane, tetrachloromethane, 1,2-dichloroethane, and trichloroethylene; hydrocarbons such as pentane, n-hexane, hexane isomer mixtures, heptane, octane, petroleum benzine, petroleum ether, benzene, toluene and xylene; ketones such as acetone, methyl ethyl ketone, diisopropyl ketone and methyl isobutyl ketone (MIBK); esters such as ethyl acetate, butyl acetate, propyl propionate, ethyl butyrate and ethyl isobutyrate; carbon disulfide; and nitrobenzene, or mixtures of these solvents.
All the symbols in the above formulae have their meanings in each case independently of one another.
In the following examples, unless stated otherwise, all amounts and percentages are by weight, all pressures are 0.10 MPa (abs.) and all temperatures are 20xc2x0 C.